1. Field of the Invention
The present invention is an orientation device (tilt switch) for use in the closed circuit television (CCTV) industry to positively resolve the physical orientation of a mechanical assembly, particularly surveillance cameras. Resolution of the physical orientation allows the operating functions of the assembly to be specifically tailored according to the orientation.
2. Description of the Prior Art
Surveillance cameras are deployed in a wide variety of enclosures and environments. In many cases, the environment will dictate the type, size and style of enclosure that is deployed. Enclosures deployed indoors are often ceiling, wall or floor mounted, and typically include a transparent dome that surrounds the surveillance camera. These enclosures may not require the environmental protections called for in outdoor or industrial deployments. Enclosures deployed outdoors or in industrial environments may be exposed to significant changes in temperature, air pressure and humidity as well as moisture (precipitation, condensation or frost), dust, debris, corrosives and other foreign material. The enclosures exposed to such conditions must be rugged, and are often equipped with such features as waterproof seals, precipitation resistant housings, ventilation and blower mechanisms, defrosting heaters, and the like. Such enclosures may be mounted on surfaces such as walls, ceilings, soffits or floors or may be attached to other structures such as poles, eaves or beams.
A given enclosure may be available for either indoor or outdoor deployment and may include many of the environmental control functions as standard features. Problems have been encountered with regard to the use of heaters in surveillance camera enclosures because of the different potential orientations of the enclosures. Heaters are useful for defrosting or defogging the transparent portions of surveillance camera enclosures. Since heat naturally rises, a heater provided inside a dome-shaped enclosure will have a different effect if the enclosure is deployed such that it hangs from a ceiling, as compared to the same enclosure deployed on a floor or on top of a flat surface.
In particular, when a heater is activated on a ceiling-mounted domed enclosure, much of the heat will rise and escape from the enclosure with very little heat actually reaching the dome. By contrast, when a heater is activated on a floor-mounted domed enclosure, much of the heat will collect inside the dome itself. Accordingly, on the ceiling-mounted enclosure, it may be necessary to operate the heater longer or at a higher temperature in order to heat the dome; whereas, on the floor-mounted enclosure much less heat and/or lower temperatures are required. If excessive heat is provided on the ceiling-mounted enclosure, the camera electronics could overheat affecting the camera performance. If excessive heat is provided on the floor-mounted enclosure, the upper portion of the transparent dome may deform, melt, or be otherwise affected interfering with and impairing the ability of the camera to obtain clear images through that part of the dome. Different degrees of these same problems are encountered with wall-mounted enclosures and with non-dome enclosures where excessive heat may collect in the upper regions of the enclosure potentially overheating the electronics or causing deforming and impairment of the optics.
Aside from heating, other environmental controls as well as camera movements and operations may also be tailored to the known positioning and orientation of the surveillance camera enclosure. In this regard, the orientation of the enclosure is also important in order to know its relationship to the ground (gravity), its position on the compass (north/south/east/west) and its position in relation to the sun.
A number of different tilt switches are known in the art. The most well known are those that use mercury that has been encapsulated inside an enclosure. Such enclosures typically have two or more electronic leads that extend into the enclosure. The liquid mercury inside the capsule moves when the enclosure is tilted. When tilted such that the mercury covers both leads, an electronic connection is made. When the enclosure is tilted in another direction, the mercury moves off one or both of the leads such that no electronic connection is made. Since mercury is a highly toxic material, mercury-based tilt switches are disfavored because of the dangers associated with any rupture of the capsule containing the mercury. Such liquid-based switches also suffer from the drawback of providing potentially erroneous information if the switch is suddenly struck or jarred.
Other known tilt switches utilize one or more balls or ball bearings disposed inside a funnel shaped housing. When the funnel is pointing down, the ball settles into the cone of the funnel where it is used to complete a circuit. When the funnel is tilted, eventually an angle is reached where the ball rolls out of the cone and disconnects the circuit. However, ball and funnel based tilt switches are expensive and not readily adaptable for wide ranging uses.
Accelerometers are also known to exist. These devices are used to measure and transmit information regarding the gravitational (“g”) forces encountered by an object. Many accelerometers utilize a spring and weight mechanism. When g forces are applied to the accelerometer, the weight compresses the spring in accordance with the amount of force applied, and this is reported electronically. Accelerometers are useful for measuring one-time events such as the dropping of an object during shipping, but are not capable of determining the angle to which an object has been tilted.
It is therefore desirable to provide a mechanism by which the orientation of a surveillance camera and/or enclosure may be determined so that appropriate instructions may be provided or programmed into the camera electronics based on the orientation in order to provide improved responses to different environmental conditions and to provide improved camera operation.